Strength training as it is traditionally performed (low number of repetitions with heavy weights) tends to cause the muscle fibers involved to enlarge (hypertrophy). There is little beneficial effect upon the cardiovascular system. Indeed, it is thought by many that a preponderance of such training may produce certain adverse effects upon the heart itself as well as untoward effects upon the arterial blood pressure.
Efforts to increase the number of repetitions and to make weight training strategies more continuous, etc., by having the exerciser move swiftly from one "station" to the next with only short pauses, have also failed to produce significant benefits with respect to endurance (aerobic) capacity. Thus subjects trained by the so-called "circuit" system, while achieving relatively high heart rates during the exercise, have not, generally speaking, increased their oxygen uptake capacity (work capacity) significantly over extended training periods.
These facts provoke the question as to whether or not strength oriented physical training can work toward the betterment of the cardiovascular system. This improvement would include such elements as slowing of the heart rate both at rest and at any greater workloads, usually lowering of the systemic blood pressure, along with various enzymatic and other metabolic changes that are readily measurable.
The crucial flaw in systems that attempt to couple strength and aerobic capacity may be their general failure to employ sufficient muscle mass during given exercises. Thus strength trainers typically work one or a few muscle groups at a time. The high heart rates achieved under those conditions do not represent the same physiologic events that general high heart rates during continuous (aerobic) exercise (jogging, brisk walking, swimming, rowing, bicycling) that employ a relatively large percentage of the body's muscle simultaneously.
There have been several devices put forth that attempt to achieve simplicity in design and do not utilize weights other than the user's own body weight for exercising. U.S. Pat. No. 4,114,873 to Jones discloses a skate exercise device. The user attaches skates to his feet for exercising various parts of the body by twisting and stretching through the movement of the legs in various back and forth or arcing motions. U.S. Pat. No. 2,819,755 to Burger, et al. discloses a physical rehabilitation device that aids a user in developing ambulatory skills. U.S. Pat. No. 277,399 to Worthington shows an exercise device of a tripodal form in which a user positions himself therein to exercise. Canadian Patent No. 993,910 to Simon shows a therapeutic traction apparatus which is akin to parallel bars but on which an individual may subject the spine to traction by suspending the body when it is suspended only by the arms. The problems with the aforementioned devices is that they do not combine the ability to couple strength and aerobic capacity. Moreover, the aforementioned devices are limited to the extent that they allow a user flexibility (range of motion) while using the device.
Circuit training systems are not alone in attempting to couple strength and aerobic capacity. One such concept which has met with much greater success in achieving the development of strength and aerobic capacity concurrently uses the idea of converting a pair of individual dumbbells to specially designed hand weights. U.S. Pat. Nos. 4,351,526; 4,627,618 L. Schwartz teach the development of strength during aerobic exercise while utilizing the hand weights. The preferred manner of exercising with the hand weights disclosed in the two patents and the one patent application to L. Schwartz is described in the publications entitled HeavyHands: The Ultimate Exercise and Heavy Hands Walking, by Leonard Schwartz, M.D. published in 1982 and 1987, respectively. While these patents disclose devices which also are capable of coupling the development of strength and aerobic capacity, they are defined upon work performed by the free motion of the hands and arms.
There is additional usefulness for an exercise apparatus that permits physical training of the body simultaneously for strength and aerobic capacity and which can be applied to all muscle groups of the body using body weight as the only resistance required. The entire bodyweight is ideally suited to serve as the resistance for strength-endurance training. This apparatus is designed to allow for the simultaneous action of a great muscle mass in lifting the body repeatedly and over relatively prolonged periods of time. This combined work, which includes a large strength component, cannot be accomplished by any combination of muscle groups activated in sequence. The apparatus structure lends itself to the careful design of combined movements and to the improvisation of such combined movements.